Treatment of macrophage mediated disease

ABSTRACT

The invention relates to a method of treating or monitoring/diagnosing a disease state mediated by activated macrophages. The method comprises the step of administering to a patient suffering from a macrophage mediated disease state an effective amount of a composition comprising a conjugate or complex of the general formula
 
A b -X
 
where the group A b  comprises a ligand capable of binding to activated macrophages, and when the conjugate is being used for treatment of the disease state, the group X comprises an immunogen, a cytotoxin, or a compound capable of altering macrophage function, and when the conjugate is being used for monitoring/diagnosing the disease state, X comprises an imaging agent. The method is useful for treating a patient suffering from a disease selected from the group consisting of rheumatoid arthritis, ulcerative colitis, Crohn&#39;s disease, inflammation, infections, osteomyelitis, atherosclerosis, organ transplant rejection, pulmonary fibrosis, sarcoidosis, and systemic sclerosis.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C §119(e) to U.S.Provisional Application Ser. No. 60/288,208, filed on May 2, 2001.

FIELD OF THE INVENTION

This invention relates to methods for treating and monitoring diseasestates mediated by activated macrophages. More particularly, ligandsthat bind to activated macrophages are complexed with an imaging agent,or an immunogen, a cytotoxin or an agent for altering macrophagefunction for administration to a diseased host for diagnosis and/ortreatment of macrophage mediated disease.

BACKGROUND AND SUMMARY OF THE INVENTION

The mammalian immune system provides a means for the recognition andelimination of foreign pathogens. While the immune system normallyprovides a line of defense against foreign pathogens, there are manyinstances where the immune response itself is involved in theprogression of disease. Exemplary of diseases caused or worsened by thehost's own immune response are autoimmune diseases such as multiplesclerosis, lupus erythematosus, psoriasis, pulmonary fibrosis, andrheumatoid arthritis and diseases in which the immune responsecontributes to pathogenesis such as atherosclerosis, inflammatorydiseases, osteomyelitis, ulcerative colitis, Crohn's disease, and graftversus host disease often resulting in organ transplant rejection.

Macrophages are generally the first cells to encounter foreignpathogens, and accordingly, they play an important role in the immuneresponse. However, activated macrophages can contribute to thepathophysiology of disease in some instances. Activated macrophagesnonspecifically engulf and kill foreign pathogens within the macrophageby hydrolytic and oxidative attack resulting in degradation of thepathogen. Peptides from degraded proteins are displayed on themacrophage cell surface where they can be recognized by T cells, andthey can directly interact with antibodies on the B cell surface,resulting in T and B cell activation and further stimulation of theimmune response.

Rheumatoid arthritis (RA) is a systemic disease characterized by chronicinflammatory synovitis, usually involving peripheral joints. Thesynovial inflammation causes cartilage deterioration and bone erosionwith consequent destruction of joint integrity. Rheumatoid factors,which are autoantibodies reactive with the Fc region of IgG, are foundin more than two-thirds of patients with RA indicating that RA has anautoimmune component.

RA is seen throughout the world in as much as 2% of the population, with80% of RA patients developing the disease between the ages of 35 and 50.The clinical manifestations of RA include pain, swelling, and tendernessin the joints resulting in limitation of motion, weakness, fatigue, andweight loss. RA is a systemic disease and, consequently, hasextra-articular manifestations, especially in patients with high titersof rheumatoid factors. These symptoms include rheumatoid nodules with aninner zone of necrotic material, a mid-zone of macrophages, and an outerzone of granulated tissue, muscle atrophy, osteoporosis, pulmonaryfibrosis, and rheumatoid vasculitis which may result in cutaneousulceration, digital gangrene, or neurovascular disease.

Rheumatoid synovitis, characteristic of RA, results in an increase inthe number of synovial lining cells, hyperplasia and hypertrophy of thesynovial lining cells, microvascular injury, edema, and infiltration ofcells such as T cells, macrophages, and dendritic cells. The rheumatoidsynovium is characterized by the presence of secreted products of immunecells such as factors secreted by T lymphocytes including IL-2, IFN-δ,IL-6, IL-10, GM-CSF and TGFα and β and factors secreted by activatedmacrophages including IL-1, IL-6, IL-8, IL-10, GM-CSF, macrophage CSF,and TGFβ. The production of these cytokines appears to account for muchof the pathology of RA including inflammation of the synovium, synovialcell proliferation, cartilage and bone deterioration, and systemicsymptoms of the disease.

RA may be treated using various therapies including physical therapy,rest, and splinting. Therapeutic agents are also used for the treatmentof RA including aspirin and nonsteroidal anti-inflammatory drugs tocontrol local inflammation. However, these agents have a minimal effecton the progression of the disease and are associated with toxic sideeffects. Disease-modifying anti-rheumatic drugs, such as α-penicillamineand sulfasalazine, are also used to treat RA, but the benefit from thesedrugs is delayed for weeks or months and these drugs have toxic sideeffects. Immunosuppressive and cytotoxic drugs suppress symptoms of RAin some patients, but are associated with toxicity. Intra-articularglucocorticoids have also been used, but provide only transient relief.Accordingly, there is a need for the development of new therapies withreduced toxicity that are efficacious for the treatment of RA and otherdiseases caused or worsened by activated macrophages.

The folate receptor (FR) is a 38 KDa GPI-anchored protein that binds thevitamin folic acid with high affinity (<1 nM). Following receptorbinding, rapid endocytosis delivers the vitamin into the cell, where itis unloaded in an endosomal compartment at low pH. Importantly, covalentconjugation of small molecules, proteins, and even liposomes to folicacid does not alter the vitamin's ability to bind the folate receptor,and therefore, folate-drug conjugates can readily enter cells byreceptor-mediated endocytosis.

Because most cells use an unrelated reduced folate carrier (RFC) toacquire the necessary folic acid, expression of the folate receptor isrestricted to a few cell types. With the exception of kidney andplacenta, normal tissues express low or nondetectable levels of FR.However, many malignant tissues, including ovarian, breast, bronchial,and brain cancers express significantly elevated levels of the receptor.In fact, it is estimated that 95% of all ovarian carcinomas overexpressthe folate receptor. It has recently been reported that FRB, thenonepithelial isoform of the folate receptor, is expressed on activated(but not resting) synovial macrophages. Thus, Applicants have attemptedto utilize folate-linked compounds potentially capable of altering thefunction of activated macrophages, to treat macrophage-mediated diseasestates. For example, Applicants have found that folate-linked immunogenscan be used to redirect the host immune response in arthritic animals toactivated macrophages at the site of inflammation to deplete macrophagesand reduce arthritic inflammation.

Scintigraphic imaging agents are a million times more sensitive thanmagnetic resonance imaging (MRI) contrast agents, and their selectivitycan be enhanced by their targeting to lesion-specific cell markers.Indeed, the radioisotope ^(99m)Tc has been delivered to arthritictissues using nonspecific IgG, anti-CD4 antibodies,CD11b/CD14-glycolipopeptide ligands, and E-selectin binding peptides.Preclinical studies with such radioimaging agents have clearlyemphasized the value of imaging arthritic tissues in-vivo, however, theselectively of the current imaging agents is not yet optimal, and noneof the present compounds is targeted exclusively to activatedmacrophages. In view of the emergence of folate receptor activity duringmacrophage activation, Applicants have undertaken to determine whether afolate-targeted ^(99m)Tc imaging agent might be used to image arthriticlesions in vivo.

To determine whether expression of this high affinity FR might beexploited to selectively target drugs to activated macrophages at sitesof inflammation, folic acid has been conjugated to a ^(99m)Tc chelator,and its distribution evaluated in both normal and diseased tissues ofrats with adjuvant-induced arthritis. The folate-linked ^(99m)Tc chelatecomplex, termed EC20, was indeed found to concentrate in the arthriticextremities of diseased rats, but not in the joints of healthy rats. Theintensity of the gamma scintigraphic images of affected tissues wasfound to be greatly reduced in the presence of excess competing folicacid. Furthermore, liver and spleen of arthritic animals also showedenhanced uptake of EC20 and increased levels of FR, confirming thatsystemic activation of macrophages accompanies adjuvant-inducedarthritis. Depletion of macrophages from arthritic animals reducedtissue FR content and concomitantly abolished uptake of EC20.Furthermore, Kupffer cells isolated from rats with adjuvant-inducedarthritis exhibited a significantly higher binding capacity for folateconjugates than Kupffer cells from healthy rats. Thus, Applicants havefound that EC20 is useful for assaying the participation of activatedmacrophages in inflammatory pathologies such as rheumatoid arthritis.

The present invention is directed to a method for treating andmonitoring disease states mediated by activated macrophages. Inaccordance with one embodiment of the present invention, disease statesmediated by activated macrophages are treated by redirecting host immuneresponses to activated macrophages or by altering the function ofactivated macrophages or by direct killing of activated macrophages. Inone aspect of the invention, to promote killing of activatedmacrophages, ligands that bind specifically to activated macrophages areconjugated with an immunogen to redirect host immune responses to theactivated macrophage population, or they are conjugated to a cytotoxinfor direct killing of macrophages. Ligands that can be used in theconjugates of the present invention include those that bind to receptorsexpressed specifically on activated macrophages, such as the folatereceptor, or ligands such as monoclonal antibodies directed to cellsurface markers specifically expressed on activated macrophages. Inanother aspect of the invention ligands that bind specifically toactivated macrophages are conjugated with an imaging agent; theconjugate is administered to a patient for diagnosing and monitoring theprogression of diseases mediated by activated macrophages.

In one embodiment, a method of treating or monitoring/diagnosing adisease state mediated by activated macrophages is provided. The methodcomprises the step of administering to a patient suffering from amacrophage mediated disease state an effective amount of a compositioncomprising a conjugate or complex of the general formula A_(b)-X, wherethe group A_(b) comprises a ligand capable of binding to activatedmacrophages, and when the conjugate is being used for treatment of thedisease state, the group X comprises an immunogen, a cytotoxin, or acompound capable of altering macrophage function, and when the conjugateis being used for monitoring/diagnosing the disease state, X comprisesan imaging agent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows folate-targeted imaging of arthritic rats (whole bodyscintigraphic images).

FIG. 2 shows folate-targeted imaging of arthritic rats (assessment ofliver, spleen and kidney by scintigraphy).

FIG. 3 shows effects of macrophage depletion (black bars representarthritic rats, light gray bars represent healthy rats, and dark graybars represent arthritic rats depleted of macrophages by clodronatetreatment).

FIG. 4 shows folate receptor-mediated uptake of EC20 in arthritictissues (light gray bars represent biodistribution of EC20 in thepresence of a 500-fold excess of free folic acid, black bars representbiodistribution of EC20 in the absence of a 500-fold excess of freefolic acid, dark gray bars represent the biodistribution of the samecomplex lacking a folate moiety (EC28)).

FIG. 5 shows folate receptor expression in various tissues of arthriticrats (black bars represent arthritic rats, light gray bars representhealthy rats, and dark gray bars represent arthritic rats depleted ofmacrophages by clodronate treatment).

FIG. 6 shows expression of a functional folate receptor on livermacrophages of arthritic rats.

FIG. 7 shows increased uptake of a folate-targeted imaging agent in apatient with an inflamed joint.

FIG. 8 shows a chemical structure representing the folate-linkedchelator EC20.

FIG. 9 demonstrates immunotherapy mediated protection againstadjuvant-induced arthritis (diamonds represent folate-FITC (left foot),squares represent PBS (left foot), triangles represent folate-FITC(right foot), and X's represent PBS (right foot)).

FIG. 10 demonstrates immunotherapy mediated protection againstadjuvant-induced arthritis (light gray diamonds represent administrationof folate-FITC, dark gray squares represent administration ofmethotrexate, dark gray triangles represent administration of saline,and black lines represent animals without arthritis). The bottom fourlines represent the uninjected paw.

FIG. 11 demonstrates immunotherapy mediated protection againstadjuvant-induced arthritis in the right (uninjected) paw (light graydiamonds represent administration of folate-FITC at 3000 nmoles/kg,light gray squares represent administration of folate-FITC at 600nmoles/kg, light gray triangles represent administration of folate-FITCat 120 nmoles/kg, light gray X's represent administration ofmethotrexate, dark gray circles represent administration in 3 doses (asin Example 14), light gray circles represent administration of saline,and black squares represent animals without arthritis).

FIG. 12 demonstrates immunotherapy mediated protection againstadjuvant-induced arthritis (black diamonds=FF, gray triangles=FF+low,vertical hash marks=FF+high, gray squares=early MTX, gray X's=late MTX,thick black lines=arthritis, gray circles=no arthritis, blackcircles=FF+mid, horizontal hash marks=late FFMTX).

FIG. 13 demonstrates immunotherapy mediated protection againstadjuvant-induced arthritis (black diamonds represent animals with noarthritis, dark gray squares represent animals with arthritis, lightgray triangles represent administration of folate-FITC, light graycircles represent administration of methotrexate, and light graydiamonds represent administration of the combination of folate-FITC andmethotrexate).

FIG. 14 demonstrates immunotherapy mediated protection againstadjuvant-induced arthritis (black diamonds=FF10, gray squares=FF2, graytriangles=FF, gray X's=IL10, black X's=IL2, open circles=PBS).

FIG. 15 shows folate-targeted imaging of arthritic rats (1^(st)bar=Healthy, 2^(nd) bar=Arthritis, 3^(rd) bar=FEFITC (FF), 4^(th)bar=MTX, 5^(th) bar=FF+low MTX). The organs are shown on the X-axis.

DETAILED DESCRIPTION OF THE INVENTION

Methods are provided in accordance with the present invention for eithertreating or monitoring/diagnosing a disease state mediated by activatedmacrophages. Exemplary of diseases known to be mediated by activatedmacrophages include rheumatoid arthritis, ulcerative colitis, Crohn'sdisease, psoriasis, osteomyelitis, multiple sclerosis, atherosclerosis,pulmonary fibrosis, sarcoidosis, systemic sclerosis, organ transplantrejection (GVHD) and chronic inflammations. Such disease states can bemonitored by first administering to a patient suffering from suchdisease state an effective amount of a composition comprising aconjugate of the general formula A_(b)-X wherein the group A_(b)comprises a ligand capable of binding to activated macrophages, and thegroup X comprises an imaging agent and thereafter scanning the patientwith an imaging device capable of detecting the imaging agent.Macrophage mediated disease states can be treated in accordance withthis invention by administering an effective amount of a composition ofthe above formula wherein A_(b) comprises a ligand capable of binding toan activated macrophage and wherein the group X comprises an immunogen,a cytotoxin, or a cytokine capable of altering macrophage function. Suchmacrophage targeting conjugates, when administered to a patientsuffering from an activated macrophage mediated disease state, work toconcentrate and associate the conjugated cytotoxin, immunogen, orcytokine with the population of activated macrophages to kill theactivated macrophages or alter macrophage function. Elimination ordeactivation of the activated macrophage population works to stop orreduce the activated macrophage mediated pathogenesis characteristic ofthe disease state being treated. The conjugate is typically administeredparenterally as a composition comprising the conjugate and apharmaceutically acceptable carrier therefor. Conjugate administrationis typically continued until symptoms of the disease state are reducedor eliminated.

In one embodiment of the invention activated macrophage mediated diseasestates are monitored or diagnosed in a patient by administering aconjugate A_(b)-X wherein A_(b) comprises a ligand capable of binding toactivated macrophages and X comprises an imaging agent and thereafterscanning the patient with an imaging device capable of detectinglocalized concentration of the imaging agent. The imaging or diagnosticconjugates are, similar to those therapeutic conjugates outlined above,typically administered as a diagnostic composition comprising aconjugate and a pharmaceutically acceptable carrier. The composition istypically formulated for parenteral administration and is administeredto the patient in an amount effective to enable imaging of the locale ofactivated macrophage populations. The nature of the imaging agentcomponent of the conjugate is dictated by the imaging methodology. Thus,for example, the imaging agent can comprise a chelating moiety and ametal cation, for example, a radionuclide or a nuclear resonance imagingcontrast agent, such as gadolinium. Typically the activated macrophagetargeted imaging agent is administered to a patient, and following aperiod of time to allow delivery and concentration of the imaging agentin the activated macrophage cell populations, the patient is subjectedto the imaging procedure and imaging is enabled by the targeted imagingagent.

The method of the present invention can be used for both human clinicalmedicine and veterinary applications. Thus, the host animals afflictedwith the activated macrophage mediated disease state can be humans, orin the case of veterinary applications, they can be laboratory,agricultural, domestic or wild animals. The conjugates administered inaccordance with the methods of this invention are preferablyadministered parenterally to the animal or patient suffering from thedisease state, for example, intradermally, subcutaneously,intramuscularly, intraperitoneally, or intravenously. Alternatively, theconjugates can be administered to the animal or patient by othermedically useful procedures and effective doses can be administered instandard or prolonged release dosage forms, such as a slow pump. Thetherapeutic method of the present invention may be used alone or incombination with other therapeutic methods recognized for the treatmentof macrophage mediated disease states.

In the ligand conjugates of the general formula A_(b)-X in accordancewith the present invention, the group A_(b) is a ligand capable ofbinding to activated macrophages. Any of a wide number of macrophagebinding moieties can be employed. Acceptable ligands includeparticularly folate receptor binding ligands and antibodies or antibodyfragments capable of recognizing and specifically binding to surfacemoieties uniquely or preferentially expressed or presented in/onactivated macrophages. In one embodiment the activated macrophagebinding ligand is folic acid, a folic acid analog or other folatereceptor binding molecules. Activated macrophages express a 38 LDGPI-anchored folate receptor that binds folate and folate-derivatizedcompounds with subnanomolar affinity (i.e., <1 nM). In anotherembodiment the activated macrophage binding ligand is a specificmonoclonal or polyclonal antibody or Fab or scFv (i.e., a single chainvariable region) fragments of antibodies capable of specific binding toactivated macrophages.

The activated macrophage targeted conjugates used for diagnosing andmonitoring disease states mediated by activated macrophages inaccordance with this invention are formed to target and, thus, toconcentrate an imaging agent at the site of activated macrophagepopulations in the diseased patient. In such conjugates of the formulaA_(b)-X, A_(b) is a ligand capable of binding to activated macrophagesand the group X comprises an imaging agent. In one embodiment theimaging agent comprises a chelating agent and a metal cation, typicallyeither a radionuclide or a nuclear magnetic resonance imaging enhanceror contrast agent, such as gadolinium. Such conjugates wherein the groupA_(b) is folic acid, a folic acid analog, or another folic acid receptorbinding ligand are described in detail in U.S. Pat. No. 5,688,488, thespecification of which is incorporated herein by reference. That patent,as well as related U.S. Pat. Nos. 5,416,016 and 5,108,921, eachincorporated herein by reference, describe methods and examples forpreparing chelate conjugates useful in accordance with the presentinvention. The present macrophage targeted imaging agents can beprepared and used following general protocols described in those earlierpatents. The present diagnostic method, however, is based in part on thediscovery that folate targeted conjugates can be used to concentrateconjugated imaging entities in and at activated macrophage populationsenabling monitoring and diagnosis of disease states characterized byconcentration of activated macrophages at the site of disease.

In accordance with one embodiment of the present invention there isprovided a method of treating disease states mediated by activatedmacrophages by administering to a patient suffering from such diseasestate an effective amount of a composition comprising a conjugate of thegeneral formula A_(b)-X wherein A_(b) is as defined above and the groupX comprises a cytotoxin, an immunogen, or a compound capable of alteringmacrophage function. Exemplary of cytotoxic moieties useful for formingconjugates for use in accordance with the present method includeclodronate, anthrax, Pseudomonas exotoxin, typically modified so thatthese cytotoxic moieties do not bind to normal cells, and other toxinsor cytotoxic agents including art-recognized chemotherapeutic agentssuch as adrenocorticoids, alkylating agents, antiandrogens,antiestrogens, androgens, estrogens, antimetabolites such as cytosinearabinoside, purine analogs, pyrimidine analogs, and methotrexate,busulfan, carboplatin, chlorambucil, cisplatin and other platinumcompounds, tamoxiphen, taxol, cyclophosphamide, plant alkaloids,prednisone, hydroxyurea, teniposide, and bleomycin, nitrogen mustards,nitrosureas, vincristine, vinblastine, inflammatory and proinflammatoryagents, and the like. Such toxins or cytotoxic components can bedirectly conjugated to the activated macrophage binding moiety, forexample, folate or other folate receptor binding ligands, or they can beformulated in liposomes which themselves are targeted as conjugates ofmacrophage binding entities typically by covalent linkages to componentphospholipids. Similarly, when the group X comprises a compound capableof altering a macrophage function, for example, a cytokine such as IL-10or IL-11, the cytokine can be covalently linked to the targeting moietyA_(b), for example, a folate receptor binding ligand or an antibody orantibody fragment directly, or the macrophage function altering cytokinecan be encapsulated in a liposome which is itself targeted to activatedmacrophages by pendent macrophage targeting entities A_(b) covalentlylinked to one or more phospholipid liposome components.

In another embodiment the ligand-immunogen conjugates can beadministered in combination with a cytotoxic compound. The compoundslisted in the preceding paragraph are among the compounds suitable forthis purpose.

In another method of treatment embodiment of the present invention thegroup X in the activated macrophage targeted conjugate A_(b)-X,comprises an immunogen, the ligand-immunogen conjugates being effectiveto “label” the population of activated macrophages responsible fordisease pathogenesis in the patient suffering from the disease forspecific elimination by an endogenous immune response or byco-administered antibodies. The use of ligand-immunogen conjugates inthe method of treatment in accordance with this invention works toenhance an immune response-mediated elimination of the activatedmacrophage population. Such can be effected through an endogenous immuneresponse or by a passive immune response effected by co-administeredantibodies. The endogenous immune response may include a humoralresponse, a cell-mediated immune response, and any other immune responseendogenous to the host animal, including complement-mediated cell lysis,antibody-dependent cell-mediated cytotoxicity (ADCC), antibodyopsonization leading to phagocytosis, clustering of receptors uponantibody binding resulting in signaling of apoptosis, antiproliferation,or differentiation, and direct immune cell recognition of the deliveredantigen/hapten. It is also contemplated that the endogenous immuneresponse will employ the secretion of cytokines that regulate suchprocesses as the multiplication and migration of immune cells. Theendogenous immune response may include the participation of such immunecell types as B cells, T cells, including helper and cytotoxic T cells,macrophages, natural killer cells, neutrophils, LAK cells, and the like.

In another embodiment, the ligand-immunogen conjugate can beinternalized and the immunogen can be degraded and presented on themacrophage cell surface for recognition by immune cells to elicit animmune response directed against macrophages presenting the degradedimmunogen.

The humoral response may be a response induced by such processes asnormally scheduled vaccination, or active immunization with a naturalantigen or an unnatural antigen or hapten, e.g., fluoresceinisothiocyanate (FITC), with the unnatural antigen inducing a novelimmunity. Active immunization involves multiple injections of theunnatural antigen or hapten scheduled outside of a normal vaccinationregimen to induce the novel immunity. The humoral response may alsoresult from an innate immunity where the host animal has a naturalpreexisting immunity, such as an immunity to α-galactosyl groups.Alternatively, a passive immunity may be established by administeringantibodies to the host animal such as natural antibodies collected fromserum or monoclonal antibodies that may or may not be geneticallyengineered antibodies, including humanized antibodies. The utilizationof a particular amount of an antibody reagent to develop a passiveimmunity, and the use of a ligand-immunogen conjugate wherein thepassively administered antibodies are directed to the immunogen, wouldprovide the advantage of a standard set of reagents to be used in caseswhere a patient's preexisting antibody titer to other potential antigensis not therapeutically useful. The passively administered antibodies maybe “co-administered” with the ligand-immunogen conjugate, andco-administration is defined as administration of antibodies at a timeprior to, at the same time as, or at a time following administration ofthe ligand-immunogen conjugate. It is contemplated that the preexistingantibodies, induced antibodies, or passively administered antibodieswill be redirected to the activated macrophages by preferential bindingof the ligand-immunogen conjugates to the activated macrophage cellpopulations, and such pathogenic cells are killed by complement-mediatedlysis, ADCC, antibody-dependent phagocytosis, or antibody clustering ofreceptors. The cytotoxic process may also involve other types of immuneresponses, such as cell-mediated immunity, as well as secondaryresponses that arise when the attracted antigen-presenting cellsphagocytose the activated macrophages and present antigens of such cellsto the immune system for elimination of other activated macrophagespresenting such antigens.

Acceptable immunogens for use in preparing the conjugates used in themethod of treatment of the present invention are immunogens that arecapable of eliciting antibody production in a host animal or that havepreviously elicited antibody production in a host animal, resulting in apreexisting immunity, or that constitute part of the innate immunesystem. Alternatively, antibodies directed against the immunogen may beadministered to the host animal to establish a passive immunity.Suitable immunogens for use in the invention include antigens orantigenic peptides against which a preexisting immunity has developedvia normally scheduled vaccinations or prior natural exposure to suchagents such as polio virus, tetanus, typhus, rubella, measles, mumps,pertussis, tuberculosis and influenza antigens and α-galactosyl groups.In such cases, the ligand-immunogen conjugates will be used to redirecta previously acquired humoral or cellular immunity to a population ofactivated macrophages in the host animal for elimination of such cells.Other suitable immunogens include antigens or antigenic peptides towhich the host animal has developed a novel immunity throughimmunization against an unnatural antigen or hapten, for example,fluorescein isothiocyanate (FITC) or dinitrophenyl and antigens againstwhich an innate immunity exists, for example, super antigens and muramyldipeptide. It is also contemplated that MHC I restricted peptides couldbe linked to the ligand for use in redirecting cellular immunity tomacrophages and eliciting T cell killing of macrophages.

The macrophage binding ligands and immunogens, cytotoxic agents,cytokines or imaging agents, as the case may be in forming conjugatesfor use in accordance with the present invention, may be conjugated byusing any art-recognized method for forming a complex. This can includecovalent, ionic, or hydrogen bonding of the ligand to the immunogen,either directly or indirectly via a linking group such as a divalentlinker. The conjugate is typically formed by covalent bonding of theligand to the targeted entity through the formation of amide, ester orimino bonds between acid, aldehyde, hydroxy, amino, or hydrazo groups onthe respective components of the complex. Alternatively, as mentionedabove, the ligand complex can be one comprising a liposome wherein thetargeted entity (that is, the imaging agent, or the immunogen, cytotoxicagent or macrophage function altering agent) is contained within aliposome which is itself covalently linked to the activated macrophagebinding ligand.

In one embodiment of the invention the ligand is folic acid, an analogof folic acid, or any other folate receptor binding molecule, and thefolate ligand is conjugated to the targeted entity by a procedure thatutilizes trifluoroacetic anhydride to prepare γ-esters of folic acid viaa pteroyl azide intermediate. This procedure results in the synthesis ofa folate ligand, conjugated to the targeted entity only through theγ-carboxy group of the glutamic acid groups of folate. Alternatively,folic acid analogs can be coupled through the α-carboxy moiety of theglutamic acid group or both the α and γ carboxylic acid entities.

Additional folate receptor binding ligands include folinic acid,pteropolyglutamic acid, and folate receptor-binding pteridines such astetrahydropterins, dihydrofolates, tetrahydrofolates, and their deazaand dideaza analogs are preferred complex-forming ligands used inaccordance with a second embodiment of this invention. The terms “deaza”and “dideaza” analogs refers to the art recognized analogs having acarbon atom substituted for one or two nitrogen atoms in the naturallyoccurring folic acid structure. For example, the deaza analogs includethe 1-deaza, 3-deaza, 5-deaza, 8-deaza, and 10-deaza analogs. Thedideaza analogs include, for example, 1,5 dideaza, 5,10-dideaza,8,10-dideaza, and 5,8-dideaza analogs. The foregoing folic acidderivatives are conventionally termed “folates,” reflecting theircapacity to bind with folate receptors, and such ligands when complexedwith exogenous molecules are effective to enhance transmembranetransport. Other folates useful as complex forming ligands for thisinvention are the folate receptor-binding analogs aminopterin,amethopterin (methotrexate), N¹⁰-methylfolate, 2-deamino-hydroxyfolate,deaza analogs such as 1-deazamethopterin or 3-deazamethopterin, and3′,5′-dichloro-4-amino-4-deoxy-N¹⁰-methylpteroylglutamic acid(dichloromethotrexate).

The conjugates used in accordance with this invention of the formulaA_(b)-X are used in one aspect of this invention to formulatetherapeutic or diagnostic compositions comprising effective amounts ofthe conjugate and an acceptable carrier therefor. Typically suchcompositions are formulated for parenteral use. The amount of theconjugate effective for use in accordance with the invention depends onmany parameters, including the nature of the disease being treated ordiagnosed, the molecular weight of the conjugate, its route ofadministration and its tissue distribution, and the possibility ofco-usage of other therapeutic or diagnostic agents. The effective amountto be administered to a patient is typically based on body surface area,patient weight and physician assessment of patient condition. Aneffective amount can range from about to 1 ng/kg to about 1 mg/kg, moretypically from about 1 μg/kg to about 500 μg/kg, and most typically fromabout 1 μg/kg to about 100 μg/kg.

When used for monitoring or diagnosis, imaging procedures are typicallycarried out about 1 to about 6 hours post administration of theactivated macrophage targeted imaging agent.

Any effective regimen for administering the ligand conjugates can beused. For example, the ligand conjugates can be administered as singledoses, or they can be divided and administered as a multiple-dose dailyregimen. Further, a staggered regimen, for example, one to three daysper week can be used as an alternative to daily treatment, and for thepurpose of defining this invention such an intermittent or staggereddaily regimen is considered to be equivalent to every day treatment andwithin the scope of this invention. In one embodiment of the inventionthe patient is treated with multiple injections of the ligand conjugatewherein the targeted entity is an immunogen or a cytotoxic agent toeliminate the population of pathogenic activated macrophages. In oneembodiment, the patient is treated, for example, injected multiple timeswith the ligand conjugate at, for example, at 12-72 hour intervals or at48-72 hour intervals. Additional injections of the ligand conjugate canbe administered to the patient at intervals of days or months after theinitial injections, and the additional injections prevent recurrence ofdisease. Alternatively, the ligand conjugates may be administeredprophylactically to prevent the occurrence of disease in patients knownto be disposed to development of activated macrophage mediated diseasestates. In one embodiment of the invention more than one type of ligandconjugate can be used, for example, the host animal may be pre-immunizedwith fluorescein isothiocyanate and dinitrophenyl and subsequentlytreated with fluorescein isothiocyanate and dinitrophenyl linked to thesame or different activated macrophage targeting ligands in a co-dosingprotocol.

The ligand conjugates are administered in accordance with this inventionparenterally and most typically by intraperitoneal injections,subcutaneous injections, intramuscular injections, intravenousinjections or intrathecal injections. The ligand conjugates can also bedelivered to a patient using an osmotic pump. Examples of parenteraldosage forms include aqueous solutions of the conjugate, for example,solution in isotonic saline, 5% glucose or other well-knownpharmaceutically acceptable liquid carriers such as alcohols, glycols,esters and amides. The parenteral compositions for use in accordancewith this invention can be in the form of a reconstitutable lyophilizatecomprising the one or more doses of the ligand conjugate. In anotheraspect of the invention, the ligand conjugates can be formulated as oneof any of a number of prolonged release dosage forms known in the artsuch as, for example, the biodegradable carbohydrate matrices describedin U.S. Pat. Nos. 4,713,249; 5,266,333; and 5,417,982, the disclosuresof which are incorporated herein by reference.

EXAMPLE 1 Materials

EC20 (a folate-linked chelator ^(99m)Tc), EC28 (the same ^(99m)Tcchelate complex without folate), and folate-fluorescein isothiocyanate(folate-FITC) were gifts from Endocyte, Inc. (West Lafayette, Ind.).Heat-killed Mycoplasma butericum was purchased from BD Biosciences(Sparks, Md.). Folic acid, light mineral oil, clodronate, collagenase-A,and streptavidin-R-phycoerythrin were obtained from Sigma Chemical Co.(St. Louis, Mo.), and Dubelco's Modified Eagle Medium (DMEM) was fromGibco-BRL (Gathersberg, Md.). ³H-folic acid was obtained from AmericanRadiolabeled Chemicals, Inc. (St. Louis, Mo.) and Microcon®-30 membraneswere purchased from Millipore Corp. (Bedford, Mass.). RK-4-biotin andED2-R-phycoerythrin antibodies were acquired from Bachem Biosciences,Inc. (Philadelphia, Pa.) and Accurate Chemical and Scientific Corp.(Westbury, N.Y.), respectively.

EXAMPLE 2 Animal Model of Arthritis

Arthritis was induced in 150-200 g female Lewis rats (Charles RiverLaboratories, Inc., Wilmington, Mass.), n=4/dose group. Briefly, 0.5 mgof heat-killed Mycoplasma butericum, suspended in mineral oil (5 mg/ml),was injected on day 0 into the left hind foot of rats followinganesthesia with ketamine and xylazine. Disease was allowed to progressfor 21 days, and animals were weighed on a daily basis to ensure thestatus of their health. All treated animals developed arthritis, asevidenced by dramatic swelling in the injected paw, progressive swellingin all noninjected limbs due to the systemic progression of arthritis,and radiographic analysis of affected limbs. All rats were maintained ona folate-deficient diet (DYETS, Inc., Bethlehem, Pa.) for 3 weeks priorto administration of folate-FITC in order to lower serum folate levelsto physiologically relevant concentrations. Control rats were alsomaintained on a folate-deficient diet but not induced to developarthritis.

EXAMPLE 3 Elimination of Endogenous Macrophages

Evaluation of macrophage independent uptake of the folate-linked imagingagent was accomplished by killing endogenous macrophages with liposomalclodronate. Liposomes were formed by rehydrating a thin film of eggphosphatidylcholine (60 mole %) and cholesterol (40 mole %) in anisotonic clodronate solution (250 mg/ml). Small unilamellar vesicleswere then generated by extrusion of the liposomes ten times through a100 nm polycarbonate membrane using a 10 ml thermobarrel extruder (LipexBiomembranes, Vancouver, Canada). Unencapsulated clodronate was removedby dialysis through a Spectrapor 300,000 M_(r)-cutoff cellulose acetatemembrane (Spectrum Laboratories, Rancho Domingues, Calif.), and theclodronate concentration in the retained liposomes was determined asdescribed in J. Microencapsul. 3(2) 109-14 (1986). Seventeen daysfollowing induction of the arthritis and three days prior toadministration of the imaging agent (EC20), rats destined for macrophagedepletion received a single intraperitoneal injection of clodronateliposomes containing 20 mg clodronate.

EXAMPLE 4 Scintigraphy and Biodistribution Analysis

Twelve hours prior to administration of imaging agent, all animalsreceived 5 ml of normal saline subcutaneously to ensure proper excretionof unbound imaging agent. Twenty-one days following induction ofarthritis, rats (n=3 per group) were injected intraperitoneally with 500μCi (2.3 nmoles/rat) of either EC20 (folate+chelator), EC20+500-foldmolar excess folic acid, or EC28 (no folate moiety). Four hours later,rats underwent either nuclear scintigraphic imaging or biodistributionanalysis.

For scintigraphy, rats were anesthetized with ketamine and xylazine, andpositioned in ventral recumbency on the image acquisition surface. Imageacquisition was performed for one minute at a count rate of 50-75,000counts per minute using a Technicare Omega 500 Sigma 410 RadioisotopeGamma Camera. Following acquisition of whole body images, radiation ofthe upper body (above the stifles) was blocked using ⅛″ lead plates, andimages of the posterior limbs were obtained. All data were analyzedusing a Medasys™ MS-DOS-based computer equipped with Medasys™ Pinnaclesoftware.

For biodistribution analysis, rats were euthanized by intraperitonealinjection of nebutal or pentobarbitol sodium. Liver, spleen, heart,lungs, intestine, and kidneys were then harvested and radiation in eachtissue was determined by counting in a gamma counter (Packard BioScienceCo., Meridian, Conn.).

EXAMPLE 5 Assay of Tissue Folate Receptor Levels

Folate receptor levels in each tissue were determined follows. Briefly,tissues were homogenized and cell membranes were isolated bycentrifugation. Membrane proteins were solubilized overnight,transferred into a Microcon®-30 filtration device, and incubated with 50nM ³H-folic acid. A duplicate of each sample, used to determinenon-specific binding, was also exposed to 50 nM ³H-folic acid, but inthe presence of 1000-fold excess unlabeled folic acid. After unbound³H-folic acid was washed through the membrane, membrane protein withbound ³H-folic acid was recovered and counted in a scintillation counter(Packard BioScience Co.) to determine the number of active folatereceptors per gram of tissue.

EXAMPLE 6 Identification of the Folate Receptor Expressing Cell Type inLiver

Arthritic and healthy rats were first anesthetized with ketamine andxylazine, and then a midline incision was made, starting in the lowerabdomen and extending through the thoracic cavity. A 24-gauge catheterwas inserted into the hepatic vein, and a 24-gauge needle was insertedin the cardiac left ventricle to serve as an outlet for the perfusionfluid. Rats were then perfused by delivery of normal saline, followed bycollagenase A solution (0.05% in Gey's balanced salt solution) throughthe catheter. Each solution was perfused for two minutes at a rate of 20ml/minute. Immediately after perfusion, livers were removed and themembranous outer tissue was dissected away. The remaining gelatinoustissue was suspended in collagenase-A solution (0.025% in DMEM) andincubated at 37° C. for two hours in the presence of 1 μM folate-FITC or1 μM folate-FITC+1 mM folic acid. Cells were then washed three times toremoved unbound folate-FITC and immediately prepared for flow cytometry.

EXAMPLE 7 Flow Cytometry Sample Preparation and Analysis

Liver cell preparations, which had been exposed to folate-FITC, weretreated for 10 mm at 4° C. with ammonium chloride lysis buffer (150 mMNH₄Cl, 10 mM KHCO₃, 1 mM EDTA, pH 7.4) to lyse red blood cells.Following three washes with phosphate buffered saline, the remainingcells were incubated for 1 h at 4° C. with either ED2R-Phycoerythrin-labeled mouse anti-rat macrophage antibody, or RK-4biotin-labeled mouse-anti rat granulocyte antibody. Cells were againwashed two times, and those that had received the biotinylated primaryantibody were further incubated with streptavidin-R-Phycoerythrin for 30minutes. Following two final washes, cells were examined for FITC andphycoerythrin dual color staining on a FACScan Coulter XL flowcytometer.

EXAMPLE 8 Immunotherapy Mediated Protection Against Adjuvant-InducedArthritis

The protocol described in Example 2 for arthritis induction wasfollowed. The efficacy of a folate-FITC conjugate (folate-fluoresceinisothiocyanate conjugate) against adjuvant-induced arthritis in rats wasinvestigated. Each rat used in the experiment was immunized at the baseof the tail with FITC-KLH (150 μg) to induce antibodies against FITC ondays −38 and −10 before administration of Mycoplasma butericum(adjuvant) to induce arthritis. The immunization of FITC-KLH was done incombination with an adjuvant (i.e., such as TITERMAX® GOLD (150 μg),Alum (150 μg), or GPI-100 (150 μg) which are all adjuvants to induceantibodies against FITC as opposed to the adjuvant used to inducearthritis). The immunized animals were then injected on day 0 in theleft foot pad with 0.5 mg of heat-killed Mycoplasma butyricum (adjuvant)to initiate development of arthritis. Then on days 1, 2, 3, 9, 11, and14, post-adjuvant (Mycoplasma butyricum) injection, the rats wereinjected intraperitoneally with either saline (control rats) or 2000nmoles/kg of folate-FITC (FF). Calipers were used to measure left andright foot dimensions daily. With reference to FIG. 9, thosemeasurements are plotted for both the adjuvant-injected feet (top twocurves) and the non-treated feet (bottom two curves). A sudden increasein swelling of the adjuvant-injected feet is due to influx ofneutrophils which have no folate receptors. Consequently, theimmunotherapy has no impact on this phase of paw swelling. However,after about 10 days, activated macrophages invade both injected feet anduninjected feet, causing bone degradation and further inflammation.These activated macrophages have functional folate receptors, and, asshown, they are eliminated or reduced by binding folate-haptenconjugates such as folate-FITC.

EXAMPLE 9 Folate-Targeted Imaging of Arthritic Rats

The protocols described in Examples 2 and 4 were followed. As notedabove, activated but not resting macrophages express a receptor for thevitamin folic acid. To determine whether folate might be exploited totarget ^(99m)Tc to sites of arthritic inflammation, EC20, afolate-linked chelator of ^(99m)Tc (see FIG. 8) was administeredintraperitoneally to rats (n=5/group) and scintigraphic images wereacquired with a gamma camera. Due to the rapid clearance of EC20,excellent contrast was obtained by at least four hourspost-administration (FIG. 1). Importantly, whole body uptake wassignificantly more intense in arthritic rats compared to healthy rats,and this uptake was greatly reduced when EC20 was administered togetherwith a saturating dose of free folic acid. This suggests that uptake byall tissues is primarily determined by a folic-specific receptor.

Intense organ uptake of EC20 prevented visualization of limbs in wholebody images of the arthritic rats. However, images of posterior limbscould be easily acquired when mid and upper body radiation was shielded.With such shielding, arthritic limbs displayed much greater EC20 uptakethan healthy extremities, and this uptake was completely eliminated inthe presence of excess free folic acid (FIG. 1). Furthermore, the leftrear foot of the arthritic animals, where inflammation was most severe,displayed greater uptake than the less severely affected right rear foot(FIG. 1).

From the whole body images, it could be concluded that abdominal organswere responsible for a majority of EC20 uptake in the arthritic animals.To confirm this assessment, liver, spleen and kidney were removed andimaged separately (FIG. 2). Livers of arthritic rats demonstrated thehighest uptake of EC20, while livers of healthy rats displayed minimaluptake. Only those spleens taken from arthritic rats could bevisualized. Free folic acid completely blocked EC20 uptake in liver andspleen, however, the free vitamin only partially decreased uptake by thekidney.

EXAMPLE 10 Effects of Macrophage Depletion

The protocols described in Examples 2, 3, and 4 were followed, exceptthat 0.25 mCi of EC20 was administered. In order to determine whethermacrophages might be responsible for the uptake of EC20, residentmacrophages were systemically eliminated from arthritic rats using aliposomal clodronate preparation (n=3 rats/group). By four days afterclodronate treatment, evaluation of paw size revealed thatclodronate-treated rats were significantly less inflamed than untreatedrats (data not shown). To determine whether macrophage elimination wouldinfluence uptake of the folate-linked imaging agent, EC20biodistribution analysis was then performed on the clodronate-treatedrats and compared to the same analysis of both healthy rats andarthritic rats not treated with clodronate. As shown in FIG. 3 (blackbars represent arthritic rats, light gray bars represent healthy rats,and dark gray bars represent arthritic rats depleted of macrophages byclodronate treatment), depletion of macrophages decreased liver uptakeof EC20 ˜20-fold in arthritic rats, while retention in the spleen andintestine was reduced by a factor of three. In most tissues, clodronatetreatment depressed EC20 uptake even below those levels observed inhealthy rats, confirming the hypothesis that activated macrophagesaccount for most of EC20 retention in normal tissues. In contrast,kidney uptake of EC20 was elevated in rats depleted of macrophages, mostlikely because the decreased internalization of EC20 by activatedmacrophages rendered more EC20 available for binding to kidney folatereceptors.

EXAMPLE 11 Folate Receptor-Mediated Uptake of EC20 in Arthritic Tissues

The protocols described in Examples 2 and 4 were followed. Twoadditional biodistribution studies were conducted to confirm that EC20uptake by tissues of arthritic rats is mediated by the folate receptor(n=3 rats/group). First, the biodistribution of EC20 was examined in thepresence (light gray bars) and absence (black bars) of a 500-fold excessof free folic acid. As seen in FIG. 4, almost complete elimination ofEC20 uptake was observed in all tissues except kidney, indicating thatbinding was indeed mediated by a folate receptor. In fact, excess folicacid competitively reduced EC20 retention in liver, spleen, heart, lung,intestine and blood to near background levels (FIG. 4). Second, toconfirm the role of folate in EC20-mediated targeting of the chelated^(99m)Tc, the biodistribution of the same complex lacking a folatemoiety (EC28) was also examined (dark gray bars). As also displayed inFIG. 4, uptake of EC28 was negligible in all tissues except kidney,where retention of the non-targeted complex was similar to that of EC20in the presence of competing folic acid.

EXAMPLE 12 Folate Receptor Expression in Various Tissues of ArthriticRats

The protocols described in Examples 2, 4, and 5 were used. The aboveresults suggest that the folate receptor is responsible for tissueuptake of EC20. In order to confirm this, Applicants attempted todirectly quantitate the folate binding protein in various rat tissues.Active folate receptor could be detected in each of the major organsexamined, and FR levels were significantly increased in arthritic rats(FIG. 5; black bars=arthritic rats; light gray bars=healthy rats).Further, FR content correlated well with uptake of EC20 seen in thebiodistribution studies. In fact, the FR assay revealed roughlyequivalent levels of receptor in arthritic liver and spleen, inaccordance with the similar uptake of EC20 by the same organs (FIG. 4).Significantly, systemic elimination of macrophages by clodronatetreatment (dark gray bars) lowered folate receptor levels in allarthritic tissues (FIG. 5), also in good agreement with the EC20biodistribution analysis. Finally, the FR assay confirmed that neitherinduction of arthritis nor clodronate treatment alters the levels of FRin kidney or heart, where FR is not thought to be associated withactivated macrophages.

EXAMPLE 13 Expression of a Functional Folate Receptor on LiverMacrophages of Arthritic Rats

The protocols described in Examples 2, 4, 6 and 7 were used. To furtherconfirm that the elevated uptake of EC20 in livers of arthritic rats isdue to a macrophage population, livers were resected fromcollagenase-perfused rats and their disaggregated cells examined forfolate conjugate uptake, using folate-FITC as a fluorescent marker forFR expression. By also labeling the same liver cell suspension with anantibody specific for rat liver macrophages, it was possible todemonstrate that macrophages are indeed the cell type that expresseselevated levels of folate receptor in arthritic animals (FIG. 6). Thus,flow cytometric analysis revealed that 70% of the liver macrophages ofarthritic rats bound folate-FITC compared to only 30% of the livermacrophages of healthy rats (FIG. 6). Further, the FITC intensity of thearthritic macrophages was higher than that of macrophages from healthylivers. Since binding of folate-FITC was suppressed in the presence ofan excess of free folic acid (1 mM), we concluded that uptake of thefolate conjugate by liver macrophages was mediated by the folatereceptor.

Using an antibody specific for granulocytes, we also examined whethertissue infiltrating neutrophils might take up folate conjugates.Although very few neutrophils were found in the liver, those that weredetected exhibited no binding capacity for folate-FITC (data not shown).Mac-1+ peripheral blood cells were also tested and similarly found tohave no binding affinity for the folate-conjugate (data not shown). Infact, no peripheral blood cells sorted positive for FITC fluorescence,suggesting that only resident tissue macrophages (and clearly only asubpopulation of those) express FR in the liver.

Finally, to begin to explore whether activated macrophages might betargeted with folate-linked drugs in human patients, we obtainedpermission to examine the whole body images of the 28 suspected ovariancancer patients enrolled in a recently completed clinical trial of thegamma imaging agent, ¹¹¹In-DTPA-Folate. As shown in FIG. 7, one patientdisplayed significant imaging agent uptake in the right knee, but notthe left knee. Importantly, no other patients demonstrated anymeasurable joint uptake. Upon request, the attending physician contactedthe anonymous patient and inquired whether she had been experiencing anychronic joint discomfort. The physician responded that the patientreported arthritis in the right knee.

Discussion

Activated macrophages are thought to be intimately involved in thepathogenesis of rheumatoid arthritis. Activated macrophages directlydestroy joint tissue by secreting metalloproteinases andattracting/activating other immune cells by releasing cytokines. Thequantitation of activated macrophages in joint tissues might be ofdiagnostic value, since activated macrophage content correlates wellwith articular destruction and poor disease prognosis in humans.

Gamma camera scintigraphy of rats receiving EC20 demonstrated thatarthritic appendages are indeed illuminated by folate-targeted ^(99m)Tc.In contrast, the legs and feet of healthy rats could not be visualized,demonstrating the selectivity of the imaging agent for arthritisapplications. Although the intensities of internal organs also increasedin adjuvant-induced arthritis, interference from such tissues did notappear to compromise the methodology, since gamma radiation frominternal, organs could be easily screened. The fact that excellentcontrast can be obtained within one to two hours of EC20 injectionfurther shows that imaging agent administration, gamma camerascintigraphy, and image analysis can be completed during the sameexamination.

Systemic activation of macrophages has been documented in rats withadjuvant-induced arthritis. Thus, it was important to establish thespecific participation of macrophages in the elevated uptake of EC20,since a folate-targeted imaging agent had never previously been examinedin arthritic animals. Three experiments were conducted for this purpose.First, clodronate-loaded liposomes were employed to systemically depletemacrophages from the treated rats. Not only were the resulting tissue FRlevels greatly reduced, but uptake of EC20 in the macrophage-rich organswas also nearly eliminated, suggesting that resident macrophages canindeed account for both FR expression and EC20 retention in the RESorgans. Second, liver cells were disaggregated by collagenase treatmentand individual cells were evaluated for folate conjugate uptake. Asnoted in FIG. 6, the vast majority of cells testing positive for folateconjugate uptake also sorted positive for the macrophage marker, ED2,confirming that FR is indeed present on the macrophages. Finally,because other immune and myelocytic cells are known to be elevated intissues of rats with adjuvant-induced arthritis, it was conceivable thatstill another extravasating blood cell type might be involved in theuptake of EC20. However, neither liver-infiltrating granulocytes nor anyblood cell in circulation displayed any capacity to bind folate-FITC.Thus, activated macrophages would seem to be the predominant cell typeinternalizing folate conjugates in the organs of arthritic rats.

It was surprising to find that up to 30% of the liver macrophages inhealthy rats also expressed the folate receptor (FIG. 6). Since afunctional folate receptor is not found on resting synovial macrophages,it is tempting to speculate that the folate-FITC binding fraction in thehealthy rats might also constitute an activated population. Twoobservations may support this conjecture. First, activated macrophagesare also found in healthy tissues following exposure to immunestimulants such as foreign antigens. Given the role of the liver inclearing foreign substances from the body, a low level of residentmacrophage activation does not seem unreasonable. Second, thefolate-FITC (and EC20) binding population of liver cells increasedsignificantly upon induction of localized inflammation and systemicmacrophage activation.

With the ability to exploit folate to deliver attached molecules toactivated macrophages now established, folate-linked imaging agents willallow the early development or continued progression of rheumatoidarthritis to be assessed. Since graft versus host disease, multiplesclerosis, Crohn's disease, ulcerative colitis, psoriasis,osteomyelitis, and even atherosclerosis may also be caused/aggravated byactivated macrophages, it is possible that the diagnosis/evaluation ofthese diseases could be aided by a folate-linked imaging/contrast agent.The avid folate conjugate uptake by activated macrophages in botharthritic joints and liver indicates that macrophages can be effectivelytargeted regardless of their anatomical location.

EXAMPLE 14 Immunotherapy Mediated Protection Against Adjuvant-InducedArthritis

For the assay shown in FIG. 10, the protocol described in Example 8 wasfollowed except that 3000 nmoles/kg of folate-FITC was administered perday (3 doses on days 1, 2, and 3) and folate-FITC was delivered using anosmotic pump implanted into the peritoneal cavity of the rat.Methotrexate (MTX) was administered at a dose of 0.15 mg byintraperitoneal injection one time per day on days 1, 8, and 15 afteradjuvant administration. MTX was used in place of folate-FITC foranimals treated with MTX. The results for both the left (injected) andright (uninjected) paw are shown. The results show that folate-FITC (FF)inhibits adjuvant-induced arthritis as well as MTX.

EXAMPLE 15 Immunotherapy Mediated Protection Against Adjuvant-InducedArthritis

The protocol described in Example 14 was followed except that only theright paw volume was measured and folate-FITC (FF) was administered atdoses of 3000, 600, and 120 nmoles/kg (FIG. 11). Also, FF wasadministered at 3000 nmoles/kg in either three doses as in Example 14(indicated as “3 doses” in FIG. 11) or on days 1, 2, 3, 9, 11, and 14 asdescribed in Example 8 (indicated as “FF3000” in FIG. 11). The resultsshow that FF inhibits adjuvant-induced arthritis in the right paw of thearthritic rats (inflammation presumably appears in the uninjected rightpaw due to the systemic progression of arthritis), and that prolongedtreatment with FF is more effective than 3 initial doses for treatmentof adjuvant-induced arthritis.

EXAMPLE 16 Immunotherapy Mediated Protection Against Adjuvant-InducedArthritis

The protocol described in Example 8 was followed except MTX was used ata dose of 0.15 mg (FF+low, early MTX, late MTX and lateFFMTX) to treatsome animals in place of FF (see FIG. 12). Other animals were treatedwith 0.75 mg of MTX (FF+mid) or 1.5 mg of MTX (FF+high). For “early MTX”treatments, the rats were injected with MTX on days 1, 8, and 15 afterarthritis induction. For “late MTX” treatments, the rats were injectedwith MTX on days 8 and 15 after adjuvant administration. Allmeasurements were of the uninjected right paw. The results show thatfolate-FITC (FF) in combination with MTX (early or late treatments and alow, high, or middle dose of MTX) inhibits adjuvant-induced arthritisbetter than FF alone.

EXAMPLE 17 Immunotherapy Mediated Protection Against Adjuvant-InducedArthritis

For the results shown in FIG. 13, the protocol described in Example 8was followed except that some animals were treated with MTX alone (0.15mg) on days 1, 8, and 15 after arthritis induction or were treated withMTX (0.15 mg; days 1, 8, and 15) in combination with FF as described inExample 14. The results show that the combination of FF and MTX inhibitsadjuvant-induced arthritis to a greater extent than MTX or FF alone.

EXAMPLE 18 Immunotherapy Mediated Protection Against Adjuvant-InducedArthritis

The protocol described in Example 8 was followed except that IL-10(10,000 U; FF10) or IL-2 (3 μg/kg; FF2) was administered along with thetreatments with FF (i.e., the cytokines were administered byintraperitoneal injections on days 1, 2, 3, 9, 11, and 14 after adjuvantadministration; see FIG. 14). The measurements made were measurements ofthe right, noninjected paw. The results show that either IL-10 or IL-2prevent the inhibition of adjuvant-induced arthritis resulting fromtreatment with FF. All of the above immunotherapy results taken togetherindicate that folate-linked agents which are cytotoxic for macrophagescan be used to treat macrophage-mediated disease states.

EXAMPLE 19 Folate-Targeted Imaging of Arthritic Rats

For the assay shown in FIG. 15, the protocols were as described inExamples 2 and 4 except that some animals were treated with FF (2000nmoles/kg; days 1, 2, 3, 9, 11, and 14) or MTX (0.15 mg; days 1, 8, and15) as described in Examples 8 and 14, respectively. The results showthat FF or MTX prevent EC20 uptake in all organs examined except thekidney. It is likely that EC20 uptake is reduced in most organs makingmore EC20 available for excretion through the kidney accounting for theincrease in EC20 detected in kidney tissues.

1. A method of treating a disease state selected from the groupconsisting of arthritis, ulcerative colitis, atherosclerosis, and lupuserythematosus, said method comprising the step of administering to apatient suffering from the disease state an effective amount of acomposition comprising a conjugate or complex of the general formulaA_(b)-X where the group A_(b) comprises folate, wherein folate binds tothe folate receptor and wherein the group X comprises fluoresceinisothiocyanate and wherein the conjugate or complex is administered toelicit an antibody response in the patient.
 2. The method of claim 1wherein the disease state is arthritis.
 3. The method of claim 1 whereinthe disease state is ulcerative colitis.
 4. The method of claim 1wherein the disease state is lupus erythematosus.
 5. A method oftreating a disease state mediated by activated macrophages selected fromthe group consisting of arthritis, ulcerative colitis, atherosclerosis,and lupus erythematosus, said method comprising the step of,administering to a patient suffering from the macrophage mediateddisease state an effective amount of a composition comprising aconjugate or complex of the general formulaA_(b)-X  where the group A_(b) comprises folate, wherein the folatebinds to the folate receptor and is capable of binding to the activatedmacrophages and the group X comprises a hapten selected from the groupconsisting of a fluorescein and a polynitrophenyl; and wherein theconjugate or complex is administered to elicit an antibody response inthe patient.
 6. The method of claim 5 wherein the hapten is selectedfrom the group consisting of fluorescein isothiocyanate anddinitrophenyl.
 7. The method of claim 6 wherein the disease state isarthritis.
 8. The method of claim 6 wherein the disease state isulcerative colitis.
 9. The method of claim 6 wherein the disease stateis lupus erythematosus.
 10. The method of claim 6 wherein the diseasestate is atherosclerosis.
 11. The method of claim 1 wherein the diseasestate is atherosclerosis.
 12. The method of claim 5 further comprisingthe step of administering an adjuvant to the patient.
 13. The method ofclaim 5 wherein the disease state is arthritis.
 14. The method of claim5 wherein the disease state is ulcerative colitis.
 15. The method ofclaim 5 wherein the disease state is lupus erythematosus.
 16. The methodof claim 5 wherein the disease state is atherosclerosis.
 17. The methodof claim 5 wherein the polynitrophenyl is selected from the groupconsisting of dinitrophenyls and trinitrophenyls.